The present invention relates to a method for estimating the position of an actuator body in an electromagnetic actuator to control a valve of an engine.
As is known, at present there are internal-combustion engines which are at the experimental stage, of the type described in Italian patent application B099A000443, filed on Aug. 4, 1999, in which the movement of the intake and exhaust valves is performed by electromagnetic actuators.
These electromagnetic actuators have undoubted advantages, in that they make it possible to control each valve according to an optimised law for any operative condition of the engine, whereas conventional mechanical actuators (typically cam shafts) require the definition of a profile of raising of the valves, which represents an acceptable compromise for all the possible conditions of operation of the engine.
An electromagnetic actuator for an internal-combustion engine of the above-described type normally comprises at least one electromagnet, which can displace an actuator body, which is made of ferromagnetic material, and is connected mechanically to the rod of the respective valve. In order to apply to the valve a particular law of motion, a control unit pilots the electromagnet with a current which is variable over a period of time, in order to displace the actuator body in an appropriate manner.
Experimental tests have shown that in order to obtain relatively high accuracy in the control of the valve, it is necessary to control the position of the actuator body with feedback; it is thus necessary to have an accurate reading, substantially in real time, of the position of the actuator body itself.
In electromagnetic actuators of the above-described type, the position of the actuator body is read by means of a laser sensor, which, however, is costly, delicate, and difficult to calibrate, and is therefore unsuitable for use in mass production.
The object of the present invention is to provide a method for estimating the position of an actuator body in an electromagnetic actuator to control a valve of an engine, which is free from the disadvantages described, and which in particular is easy and economical to implement.
According to the present invention, a method is provided for estimating the position of an actuator body in an electromagnetic actuator to control a valve of an engine, as described in claim 1.
The present invention also relates to a device for estimating the position of an actuator body in an electromagnetic actuator to control a valve of an engine.
According to the present invention, a device is provided for estimating the position of an actuator body in an electromagnetic actuator to control a valve of an engine, as described in claim 9.